Solid film lubricant, method for producing same, sliding element comprising same and use thereof

Abstract

The invention relates to an imide polymer-based solid film lubricant, a method for producing same, a sliding element comprising same and the use thereof. According to the method, difunctional or cyclized difunctional compounds and optionally functional fillers are added to a non-imidized or partly imidized polyamide acid prepolymer or an imidized short-chain blocked prepolymer in a solvent or solvent mixture and then, depending on the prepolymer, a polymerization reaction or an imidization reaction and in both cases a crosslinking reaction is carried out. The solid film lubricant comprises an imide polymer as the resin matrix and optionally functional fillers, the molecules of the imide polymer comprising groups (R1) of the difunctional compounds that additionally contribute to the crosslinking.

The invention claimed is: 
     
       1. A method for producing an anti-friction lacquer on the basis of an imide polymer as a resin matrix of the lacquer comprising: adding bi-functional or cyclized bi-functional compounds to one of a selected non-imidised or partially imidised polyamide acid prepolymer or an imidised, short-chained blocked prepolymer in a solvent or solvent admixture, wherein the solvent or solvent admixture contains polar, aprotic solvents; and subsequently, in accordance with the selected prepolymer, carrying out a polymerization or an imidisation reaction and in either case a cross-linking reaction to produce the lacquer, wherein the bifunctional or cyclised bifunctional compounds crosslink the non-imidised or partially imidised polyamide acid prepolymer or the imidised, short-chained blocked prepolymer. 
     
     
       2. The method according to  claim 1 , including selecting a quantity of the bi-functional or cyclized bi-functional compounds to be at least 1 mol % in relation to the number of potential imide groups of the polyamide acid prepolymer or in relation to the number of present imide groups of the short-chained blocked prepolymer, and/or in that the quantity of the added bi-functional or cyclized bi-functional compounds is at a maximum 35 mol % in relation to the number of potential imide groups of the polyamide acid prepolymer or in relation to the number of present imide groups of the short-chained blocked prepolymer. 
     
     
       3. The method according to  claim 2 , wherein the quantity of the bi-functional or cyclized bi-functional compounds ranges from 3 to 25 mol % in relation to the number of potential imide groups of the amide acid prepolymer or in relation to the number of present imide groups of the short-chained blocked prepolymer. 
     
     
       4. The method according to  claim 1 , wherein the polyamide acid prepolymer or the short-chained blocked prepolymer is selected from the group of prepolymers for producing polyimides (PI), polyamideimides (PAI), polyether imides (PEI) and polyester imides. 
     
     
       5. The method according to  claim 1 , wherein the bi-functional or cyclized bi-functional compounds are selected from aromatic or aliphatic or aromatic-aliphatic compounds of the group comprising diamines, diamides, dicarboxylic acids, amino acids, lactams, lactones, imides, anhydrides, acid halides, dialcohols and hydroxyl carboxylic acids. 
     
     
       6. The method according to  claim 5 , wherein the bi-functional or cyclized bi-functional compounds have chain lengths less than 8 C atoms. 
     
     
       7. The method according to  claim 1 , wherein the solvent or solvent admixture includes at least one of NMP, NEP or additional homologue substances, DMSO, GBL, DMF, DMAC, DMEU, DMPU, MI, and MEK. 
     
     
       8. An anti-friction lacquer comprising an imide polymer as a resin matrix and functional fillers wherein the molecules of the imide polymer have residues of bi-functional or cyclized bi-functional compounds contributing to the cross-linking. 
     
     
       9. The anti-friction lacquer according to  claim 8  wherein the proportion of the functional fillers does not exceed 75% by vol. in relation to the cured anti-friction lacquer and in that the functional fillers contain one or more of the substances solid lubricants, hard material and substances which improve the thermal conductivity. 
     
     
       10. The anti-friction lacquer according to  claim 9 , wherein the solid lubricants contain one or more of the substances metal sulphides with a layered structure comprising MoS 2 , WS 2 , SnS 2 , graphite, hexagonal BN, polytetrafluoroethylene (PTFE), ZnS, BaSo 4  and admixtures thereof. 
     
     
       11. The anti-friction lacquer according to  claim 10 , wherein the hard materials contain, in a proportion not greater than 10% by vol. in relation to the cured anti-friction lacquer, one or more of the substances nitrides, carbides, borides, oxides. 
     
     
       12. The anti-friction lacquer according to  claim 10 , wherein the materials which improve the thermal conductivity contain, in a proportion not greater than 30% by vol. in relation to the cured anti-friction lacquer, one or more metal powders from the group comprising Ag, Pb, Au, Sn, Al, Bi or Cu. 
     
     
       13. The anti-friction lacquer according to  claim 8 , wherein the functional fillers contain iron (III) oxide or NiSbTi mixed-phase oxide at a quantity up to 15% by vol. in relation to the cured anti-friction lacquer. 
     
     
       14. A sliding element comprising: a metal substrate layer and a coating applied thereto of at least one anti-friction lacquer comprising;
 an imide polymer as a resin matrix and functional fillers wherein the molecules of the imide polymer have residues of bi-functional or cyclized bi-functional compounds contributing to the cross-linking, wherein the metal substrate layer comprises a steel support layer of a metal bearing metal layer, wherein the coating is applied to an exposed layer of the substrate layer, the exposed layer of the substrate layer preferably being formed from a Cu, Al, Ni, Sn, Zn, Ag, Au, Bi or Fe alloy. 
 
     
     
       15. The sliding element according to  claim 14 , including a sliding layer forming the exposed layer of the substrate layer, on which the coating is constructed as a run-in layer for conditioning a counter-movement member or as a run-in layer for adaptation, the sliding layer optionally being constructed as a sputter layer or as a galvanic sliding layer. 
     
     
       16. The sliding element according to  claim 14 , including a bearing metal layer forming the exposed layer of the substrate layer, on which the coating is constructed as a sliding layer with a long service-life. 
     
     
       17. The sliding element according to  claim 14 , including an intermediate layer of Sn, Ni, Ag, Cu, Fe or the alloys thereof forming the exposed layer of the substrate layer on which the coating is constructed. 
     
     
       18. The sliding element according to  claim 14 , wherein the coating is a multi-layered system of at least two anti-friction lacquers, including an upper anti-friction lacquer layer constructed as a run-in layer for conditioning a counter-movement member on a lower anti-friction lacquer layer as a sliding layer with a long service-life or the upper anti-friction lacquer layer is a sliding layer with good sliding and adaptation properties applied to a lower anti-friction lacquer layer which has a high level of wear resistance. 
     
     
       19. The sliding element according to  claim 14 , wherein the coating is a multi-layered system comprising at least two anti-friction lacquers including an upper anti-friction layer, of which at least one of the anti-friction lacquer layers is constructed according to  claim 14 , wherein the upper anti-friction lacquer layer which is constructed as a sliding layer with good sliding and adaptation properties or as a sliding layer which has a high level of wear resistance, and wherein between the anti-friction layer and the metal substrate layer there is provided an additional anti-friction lacquer layer which has few or no additives. 
     
     
       20. The sliding element according to  claim 14 , wherein the coating is a multi-layered system comprising at least two anti-friction lacquers, of which at least of e of the anti-friction lacquers is constructed according to  claim 14 , wherein the at least two anti-friction lacquers have different proportions at least with respect to a substance selected form the group comprising bi-functional or cyclized bi-functional compounds, solid lubricants, hard materials and materials which improve the thermal conductivity or in that the coating is a gradient layer system comprising at least two anti-friction lacquers, of which at least one anti-friction lacquer is constructed according to  claim 8 , wherein the gradient layer system when viewed over at least a portion of the layer thickness has at least one substance selected form the group comprising bi-functional or cyclized bi-functional compounds, solid lubricants, hard materials and materials which improve the thermal conductivity in an increasing or decreasing proportion. 
     
     
       21. The method of  claim 1  including adding fillers to the matrix. 
     
     
       22. The method according to  claim 3 , wherein the range is 5 to 20 mol %. 
     
     
       23. The method according to  claim 6 , wherein the lengths are less than 5c atoms. 
     
     
       24. The anti-friction lacquer of  claim 13 , wherein the vol % is 1 to 10. 
     
     
       25. The sliding element according to  claim 14 , including a metal intermediate layer. 
     
     
       26. The sliding element according to  claim 14 , including a sliding layer. 
     
     
       27. The anti-friction lacquer according to  claim 11 , wherein the hard materials contain at least one of SiC, Si 3 N 4 , B 4 C 3 , cubic BN and SiO 2 .